We had ADT for 3 years. Free install of equipment, $29.95/mo for the 2 year contract...then they started raising the rates.
Along came a salesman selling Monitronics systems...virtually identical to ours, so instead of the basic equipment install, we got a ton of upgrades to our existing system. $34.99/mo (which was $5/mo cheaper than the increased ADT rate) so we took that deal. Our 3 year contract is up and we're waiting for yet another sales rep to come wandering the neighborhood offering us MORE upgrades...
As for the two companies...I actually liked ADT's customer service better, BUT, part of why we changed when we did is because of a change in the local alarm law. Now the alarm system has to have "2-way voice" and a confirmed alarm event for the cops to respond. "Oh no sir, everything is fine. I made a mistake," sez the lady with a gun pointed at her head. :roll:
Monitronics seems a bit less responsive to customer service issues than ADT was, their reps (Dallas call center) seem like they really don't give a shit.
BUT, when that alarm goes off...they're on the 2-way immediately wanting to know if everything is ok. NO complaints about that part of the service.